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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #242172

Title: Genome Diversity and Intra- and Inter-Species Recombination Events in Grapevine fanleaf virus

Author
item MEKURIA, T - WASHINGTON STATE UNIVERSITY
item GUTHA, L - WASHINGTON STATE UNIVERSITY
item MARTIN, ROBERT
item NAIDU, R - WASHINGTON STATE UNIVERSITY

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2009
Publication Date: 12/1/2009
Citation: Mekuria, T., Gutha, L.R., Martin, R.R., Naidu, R.A. 2009. Genome diversity and intra- and inter-species recombination events in Grapevine fanleaf virus . Phytopathology. 99(12)1394-1402.

Interpretive Summary: Grapevine fanleaf virus (GFLV) was detected in four wine grape cultivars grown as self-rooted vines. GFLV was found as a mixed virus infection in Pinot Noir and Chardonnay, but not in Merlot and Cabernet Franc. Fanleaf disease symptoms were observed only in the first two cultivars. The distribution of GFLV-infected grapevines was random in vineyards, which suggests that the virus was introduced with infected cuttings and has not spread within the field. Sequence analysis of these isolates of GFLV suggests that interspecies recombination occurs in RNA2 of grapevine-infecting nepoviruses, which could be an important strategy for GFLV evolution. From a practical point of view, the generation of viral chimeras could lead to increased genetic diversity and result in the emergence of virus variants that differ in biological properties from common isolates prevailing in a grape-growing area. These new variants are poorly distinguishable by ‘reliable’ serological tests and might severely compromise our ability to gather a true picture of virus variability. Thus, molecular studies such as sequencing of complete genomic RNAs will contribute to an understanding of nepovirus diversification due to naturally occurring recombinations and biological studies including nematode transmissions will offer insights on epidemiological implications of such ‘novel’ variants of nepoviruses.

Technical Abstract: Grapevine fanleaf virus (GFLV) was documented in four wine grape (Vitis vinifera) cultivars grown as own-rooted vines. GFLV was found as a mixed virus infection in cvs. Pinot Noir and Chardonnay, but not in cvs. Merlot and Cabernet Franc. Fanleaf disease symptoms were observed only in the first two cultivars. The spatial distribution of GFLV-infected grapevines was random and suggestive of primary spread through planting virus-infected cuttings. RNA1 sequences of Washington isolates showed 87% to 89% sequence identity between them and with GFLV F13 isolate. RNA2 of Washington isolates was variable in size showing 85% to 99% sequence identity between them and with other GFLV isolates. Like in other GFLV isolates, three conserved putative stem-loop structures were present in the 5’ NCRs of both RNAs of Washington isolates. A pairwise comparison of RNA2 genome sequences indicated separation of Washington isolates into four genetically distinct variants. Phylogenetic incongruence of GFLV isolates from Washington in 2AHP- and 2AMP-based trees suggested that their genomic RNA2 have originated from inter- and intra-species recombination events in different gene sequences between GFLV, Grapevine deformation virus and Arabis mosaic virus. These results suggest interspecies recombination in RNA2 of grapevine-infecting nepoviruses as an important strategy for GFLV evolution.